Abstract

We combine the evanescent-field scattering sensing mechanism with the fiber-loop ringdown detection scheme to create a new type of fiber optic index sensor using partially cladded single-mode fiber as a sensing element. A detection limit for an optical index change of $3.2\times {10}^{-5}$ is demonstrated in the initial examination by using certified refractive index oils and laboratory-made sodium chloride solutions. This is the highest sensitivity for a fiber optic index sensor to date (to our knowledge) without using any chemical coating, delicate fiber components, and/or sophisticated architecture at the sensor head. A potential detection limit can be of the order of ${10}^{-6}$.

© 2010 Optical Society of America

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